Peripheral diamond abrasive wheel and method of making same



March 14, 1944. 5, c o PToN, JR

PERIPHERAL DIAMOND ABRASIVE WHEEL AND METHOD OF MAKING SAME Filed April 2, 1942 [-75.3 Fi .4 H1325 Patented Mar. 14, 1944 PERIPHERAL DIAMO D ABRASIVE WHEEL AND METHOD OF MAKING SAME George Crompton, Jr., Worcester, Mass., assignor to Norton Company, Worcester, Mass., ,a corporation of Massachusetts Application April 2, 1942, Serial No. 437,374

Claims. (01. 51-309) The invention relates to peripheral diamond abrasive wheels and methods of making them, and with regard to its more specific features to wheels having a single layer of diamonds.

One object of the invention is to provide an inexpensive peripheral diamond wheel. Another object of the invention is to provide a single layer diamond abrasive wheel of relatively long life. Another object of the invention is to provide a practical commercial method for making wheels of the class indicated which will permit the ready duplication of results.

Another object of the invention is to orient and distribute the diamonds or other abrasive grains on the peripheral surface of a backing, whereby a uniform and efficient grinding action will be secured. Another object of the invention is to provide an efllcient apparatus and method for the electrostatic deposition of diamond abrasive upon a circular backing. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, arrangements of parts, and in the several steps and relation and order of each of said steps to one or more of the others thereof, all as will be illustratlvely described herein, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawing illustrating one of many possible embodiments of the mechanical features of the invention,

Figure 1 is a vertical sectional view of apparatus for making the wheel according to the invention, some of the parts being shown in elevation;

Figure 2 is a view, on an enlarged scale, of a portion of the wheel backing showing the application first of a coating of solder and then of diamonds;

Figure 3 is a fragmentary radial sectional view of the backing showing the periphery;

Figure 4 is a view similar to Figure 3 showing a layer of solder;

Figure 5 is a view similar to Figure 4 showing a. layer of diamonds in the solder;

Figure 6 is a view similar to Figure 5 showing an additional layer of metal which has been applied, for example, by an electroplating process.

Referring first to Figure l, I provide a hopper Ill containing diamonds II and having a cover plate I! to keep out dust. A hole l3 admits air to prevent the formation of a vacuum. The hopper has at the lower part thereof approaching walls It and it and the wall ll contacts a roller 16.

source of power, not shown.

The wall it is just clear of the roller l8 and a slidable gate ll can be adjusted to more or less clearance from the roller IS. The roller I6 is on a shaft it which is fastened to a pulley l9 over which runs a belt 20 driven from any suitable driven clockwise, thus driving the roller I6 clockwise to discharge diamonds under the gate ll. This produces a waterfall of diamonds descending from the right-hand side of the roller it. The gate ll could be on the other side and the roller It could move counterclockwise to discharge the waterfall on the left-hand side of the roller It.

A suitable source of power, not shown, drives a belt 2| around a pulley 22 on a shaft 23 to which is fastened a roller 24 which is thus rotated, in this case in a counterclockwise direction. Around the roller 24 passes a belt 25 which also passes around idler rollers 26 and 21. The width of the belt 25 is substantially the same as that of the roller l6 and the belt 25 picks up the waterfall of diamonds and moves them to the left. Any

suitable tray, not shown, may be placed under the belt to catch diamonds that bounce oil the belt or fall off at the edges. The roller 21 is grounded.

Another belt 30 driven from a suitable source of power, not shown, passes around and rotates a pulley 3| which is fastened to a stud shaft 32 upon which is a nut 33 removably securing in place a wheel back 34. This wheel back is made of a suitable metal, for example, of German silver. The wheel back It is likewise shown in the remaining figures. It should be more or less of a disk having a peripheral surface 35 which is more or less of a cylinder. The width of the surface 35 should be substantially that of the width of the belt 26. The surface 35, however, may be a cone or may be undulating.

The shaft 32 is supported at the top .of a frame 48 upstanding from a base 4|. In any appropriate manner the shaft 32, nut 33, and wheel 34 areinsulated. The frame 40 may be of metal and the parts mentioned may be insulated by an insulating bearing or else all or a portion of a frame l0 may be built of insulating material. It is preferred to place the whole structure upon an insulating plate 42.

Upstanding from the base 4| is a forked bracket 45 supporting a pin 46 which pivots a foot treadle ll having an insulating tread 48. The otherend of the treadle I1 is a fork 49 having pins ill projecting into a groove 5i on the outside of a long vertical sleeve 52 which slides up and down on a shaft 53 but cannot turn thereon on account The pulley i9 is.

of a key II. The shaft II is screwed into a plate ll resting on and suitably fastened to the base I l At the upper end of the sleeve 52 is a wheel 56 having an inwardly extending flange ll engaging an outwardly extending flange it formed on the sleeve 52. On top of the sleeve 52 rests a hub GI oi the wheel 56 which is internally screw threaded and engages a screw shaft 6| which is non-rotativeiy guided in the sleeve 62 by means of a key 62. The hand wheel 55 has an insulat n outer portion 81 by which it may be turned.

To the upper end of the shaft 8| by means of a nut 65 is fastened a box 68 having openings 81 on the under side and containing a burner pipe 68 upstanding from which are a plurality of burners B9. The pipe 68 is connected by means of a rubber hose 10 with a valve, not shown and a source of gas. The rubber hose Iii serves at once as a flexible connection and another insulator.

The burners 69 extend through a hole II in the top of the box 66 and into a second box 12 which has a bottom opening 13 matching the opening ii. The box I2 contains refractory bricks 15 which are shaped to support the edges of a melting pot l5 and act both as heat insulators and electric insulators. The melting pct 16 is filled with suitable metal or solder, for example, hard German silver solder, copper 35; zinc 56.5; nickel 9.5.

In any suitable manner, that is, by the use of a bus bar and a high tension electric generating apparatus. electromotive force of high potential is maintained on the disk 34. This is diagrammatically indicated by a line 80. It was already noted that the roller 21 was grounded. The belt 25 is a dielectric material. be energized by means of the line Si or either of the l nes 80 or Bi might be connected to ground. A uni-directional field, that is, derived from a constant source of voltage, is preferably maintained but under certain conditions alternating or pulsating current might be used. The exact electromotive force used will depend upon many circumstances but for the conditions I have in mind 10,000 volts may be used.

Preferably the apparatus includes a cooling device, such as a pair of nozzles 85 on the ends of pipes 85 having valves 81 to blow cold air on the sides of the disk 34. Preferably the air should not impinge the periphery of the disk but should impinge the sides near the periphery at an acute angle to the planes of the sides of the disks.

The operation of the apparatus is as follows: The peripheral surface of the disk 34 may frst be coated with a flux. Calcined borax is a good flux for hard solder. One effective way to add the flux is to sandblast the surface 35 until it is quite rough. then rub dried borax upon the surface.

The disk 3| is now mounted upon the spindle 32. The hard solder. such as that already mentioned, is then introduced into the melting not it and the gas burners 69 are lighted. After a little time the solder melts. Then the belts 20. 2| and 3|) are started and the operator steps upon the tread 48 of the treadle 1. raising the melted soldier in the pot 18 into contact with the periphery of the disk 34. As soon as a film of liquid comes opposite the belt 25, the main switch. not shown. is closed creating the electrostatic field mentioned and at the same time the valve 87 is turned to apply the air blasts. Diamonds The roller 21 might jump from the belt 28 onto the surface 38 which is coated with a film of liquid 90. The diamonds 8| are evenly distributed and oriented in the liquid 90, as shown in Figure 5. The viscosity of the solder is high and the surface tension is great and so the diamonds do not fallout and shortly after they have contacted the liquid the solderis congealed by the air blasts. When the advance end of thediamond coating just about reaches the liquid solder in the melting pot it, the operator removes his foot from the tread 48 and lowers the pot ii. The coating operation, however, continues due to the already molten solder on the periphery 35. At this point the air blasts from the nozzles should be cut ofl to prevent premature solidification of the solder.

The hand wheel 56 with the insulating rim B3 is provided for adjusting the level of the liquid from time to time. If desired a weight 88 connected to the sleeve 52 by a cord 96 going over a pulley 91 may be provided to balance part of the weight of the apparatus to prevent the operator from being fatigued in running this apparatus.

After the wheel 34 is coated, as shown in Figure 5, it is desirable to apply a further layer, such as the layer Hill (Figure 6), of a tough metal to hold the diamonds 9| more firmly in position. A suitable metal, such as nickel, may be applied in an electroplating bath which need not be described herein, since the electroplating of nickel is known. The sides of the disk 34 can be stoppedoif during the electroplating operation.

Although a specific flux, a specific solder. a specific electroplating metal, and a specific metal for the disk 34 have been mentioned, it should b understood that other metals and combinations of metals and other fluxes may be used, The object is to anchor the diamonds 8i securely to the disk 34. How much metal is used will depend upon how free-cutting the wheel is to be or wine her, on the other hand, it should be high- 1y resistant to wear and have a long life.

By causing the diamonds 9! to impinge upon the periphe'y of the disk 34 by means of an electrostatic field, they are evenly spaced and well distributed upon the periphery and at the same time well oriented to provide good cutting edges and make a free-cutting grinding wheel. bumping or crowding of abrasive in one spot is avoided. as also are thin places.

It will thus be seen that there has been provided by this invention a method, apparatus and an article in which the various objects hereinabovc set forth together with many thoroughly practical advantages are successfully achieved. As various possible embodiments might be made of the meechanical features of the above invention andas the art herein described might be varied in various parts, all without departing from the scope of the invention, it is to be unde stood that all matter hereinbefore set forth or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. Method of making a grinding wheel comprising rotating a metal blank in a bath of molten metal while moving a supply of abrasive matorial in a continuous stream towards a surface of said metal blank which has a liquid film of metal from the metal bath, and transferring the abrasive from the stream to the metal blank by electrostatic attraction.

2. Method 0! making a grinding wheel comprising rotating a metal disk with its periphery in a molten metal bath, supplying abrasive to a conveyor which moves to a point adjacent the periphery of the metal blank, and forming an electrostatic field between the point and the periphery.

3. Method of making a grinding wheel comprising rotating a metal blank in a 'bath 0! molten metal while moving a supply 01' abrasive grains in a continuous stream to the surface of said metal blank which has a liquid film 01 metal from the molten bath, and thereafter metal plating an additional layer oi metal around the abrasive grains by an electroplating operation.

4. Method 0! making a grinding wheel comprising rotatlng a metal blank with its periphery in a bath of molten metal, feeding abrasive grains uted and oriented with their greatest dimensions radial to the blank embedded in the relatively low melting point metal and oonstrictingly engaged by said low melting point metal by intimate contact or said low melting point metal entirely around the periphery of the embedded portions of said diamonds. and a further layer of relatively high melting point metal upon the layer of low melting point metal and surroundins the diamonds.

GEORGE CROMP'I'ON. Jl. 

